I can't say enough positive things about Dana's amazing apartment at The Base condo in On Nut, where I stayed for 6 weeks.
Dana was always super-communicative and helpful. The apartment was very clean, spacious yet cosy and well furnished. It also has a great view and the Internet was fast and stable. The Base has an amazing swimming pool and a pretty good gym, there is also a pretty big 7/11 on-site, plus a restaurant and some other shops.
The location is about a 10 minute walk from On Nut BTS, the walk takes you through some interesting streets with lots of street food options! it's possible to take a moto-taxi also for 20 baht.
I highly recommend this apartment and will definitely be returning when I'm next in the area!